Sheet discharge device and sheet discharge method

ABSTRACT

A sheet discharge device includes a sheet discharge roller pair composed of an upper roller and a lower roller; and a placement tray, arranged below the sheet discharge roller pair, configured to place a sheet discharged from the sheet discharge roller pair. The device further includes a sheet presser configured to be held on a sheet discharge side of the upper roller in a movable manner and pushed up by a sheet front end to be discharged, and depress a sheet rear end with the dead weight thereof after the sheet rear end passes through a nip between the sheet discharge roller pair. The device additionally includes an auxiliary tray that is movable between a first position where the sheet rear end depressed by the sheet presser is caught and a second position where the sheet rear end is released from the sheet presser.

FIELD

Embodiments described herein relate generally to a sheet discharge device and a sheet discharge method.

BACKGROUND

In a conventional device for discharging a sheet such as a MFP (Multi-Function Peripheral), a printer, a scanner, an ADF (Auto Document Feeder), and a facsimile, there is a problem that sheets discharged to a placement tray are placed without being arranged in an orderly manner. This is mainly because a sheet protrudes from a predetermined position to be placed (hereinafter, referred to as “sheet protrusion”) due to a difference in sheet material, a change in environment, or a variation in a sheet discharge speed, or a sheet rear end is remained on a wall surface of the placement tray (hereinafter, referred to as a “remaining of the sheet rear end”).

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus comprising o sheet discharge device according to at least one embodiment;

FIG. 2 is a block diagram illustrating an example of a control system of an image forming apparatus;

FIG. 3 is a block diagram illustrating a control system of a sheet discharge control circuit;

FIG. 4A is a diagram illustrating an example in which two sheet pressers are mounted on a sheet discharge roller pair;

FIG. 4B is a diagram illustrating an example in which four sheet pressers are mounted on a sheet discharge roller pair.

FIG. 5 is a schematic diagram illustrating an auxiliary tray and an auxiliary tray driving mechanism according to some embodiments;

FIG. 6 is a flowchart for depicting a sheet discharge method;

FIG. 7A is a cross-sectional view of a sheet discharge section for showing a state in which a sheet discharge sensor detects a sheet and a sheet front end is located in front of the sheet discharge roller pair;

FIG. 7B is a cross-sectional view of the sheet discharge section for showing a state in which the sheet front end passes through the sheet discharge roller pair and pushes up the sheet presser;

FIG. 7C is a cross-sectional view of the sheet discharge section for showing a state in which the sheet rear end passes through the sheet discharge roller pair, the sheet rear end depressed by the sheet presser is caught by an auxiliary tray, and the sheet rear end is pressed between the sheet presser and the auxiliary tray;

FIG. 7D is a cross-sectional view of the sheet discharge section for showing a state in which the auxiliary tray is retracted and the sheet falls down;

FIG. 8 is a schematic diagram illustrating an auxiliary tray and an auxiliary tray driving mechanism according to some embodiments;

FIG. 9A is a cross-sectional view of the sheet discharge section for showing the state in which the sheet discharge sensor detects a sheet and the sheet front end is located in front of the sheet discharge roller pair;

FIG. 9B is a cross-sectional view of the sheet discharge section for showing a state in which the sheet front end passes through the sheet discharge roller pair and pushes up the sheet presser;

FIG. 9C is a cross-sectional view of the sheet discharge section for showing a state in which the sheet rear end passes through the sheet discharge roller pair, the sheet rear end depressed by the sheet presser is caught by the auxiliary tray, and the sheet rear end is pressed between the sheet presser and the auxiliary tray;

FIG. 9D is a cross-sectional view of a sheet discharge section for showing a state in which an auxiliary tray is retracted and a sheet falls down; and

FIG. 10 is a flowchart for depicting a method of continuously discharging sheets at a high speed.

DETAILED DESCRIPTION

In order to solve the above-described problem, there is a method of suppressing the sheet protrusion to place the sheet by pressing an upper surface of the sheet to be discharged with a flap or the like on an inclined placement tray. However, as a processing speed of an image forming apparatus such as an MFP increases, a discharge speed of the sheet also increases, and thus, the problems of sheet protrusion and a sheet rear end remaining become even more serious. A method of adjusting an inclination angle of the placement tray and the shape and weight of the flap to improve the sheet protrusion may not resolve such issues, i.e., at least the remaining of the sheet rear end may not be improved. Therefore, it is necessary to control a sheet stacking speed in order to place the sheets discharged at a high speed in an orderly manner.

In accordance with at least one embodiment, a sheet discharge device comprises a sheet discharge roller pair composed of an upper roller and a lower roller; a placement tray, arranged below the sheet discharge roller pair, configured to place a sheet discharged from the sheet discharge roller pair; a sheet presser configured to be held on a sheet discharge side of the upper roller in a movable manner and pushed up by a sheet front end to be discharged, and depress a sheet rear end with the dead weight thereof after the sheet rear end passes through a nip between the sheet discharge roller pair; and an auxiliary tray movable between a first position where the sheet rear end depressed by the sheet presser is caught and a second position where the sheet rear end is released from the sheet presser.

In accordance with some embodiments, a sheet discharge method involves pushing up a sheet presser movably held on sheet discharge side of an upper roller by a sheet front end discharged from a sheet discharge roller pair composed of the upper roller and a lower roller; depressing a sheet rear end with the dead weight of the sheet presser after the sheet rear end passes through a nip between the sheet discharge roller pair; catching the sheet rear end depressed by the sheet presser with an auxiliary tray moved to a first position; releasing the sheet rear end from the sheet presser by moving the auxiliary tray to a second position; and dropping the sheet onto a placement tray having a wall surface arranged below the sheet discharge roller pair on a conveyance upstream side.

Hereinafter, embodiments will be described with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a configuration of an image forming apparatus including a sheet discharge device according to the at least one embodiment. A MFP is described as an example of the image forming apparatus.

A MFP 1 shown in FIG. 1 includes a scanner 2, a control panel 3, a sheet feed cassette section (a sheet cassette) 4, a manual sheet feed tray 5, a printer section (a printer) 6, and a sheet discharge section (a discharger) 7. A sheet discharge device at least one embodiment may be installed in the MFP 1 as the sheet discharge section 7.

The scanner 2 reads a document image for forming an image by the printer section 6. The control panel 3 receives an input by a user, for example, or displays it to the user.

The sheet feed cassette section 4 includes a sheet feed cassette 4 a for storing a sheet P as an image receiving medium on which an image is formed and a pickup roller 4 b for picking up the sheet P from the sheet feed cassette 4 a. The manual sheet feed tray 5 feeds the sheet P by manual feeding with the pickup roller 5 a.

The sheet P has a sheet shape, and in the case of MFP, it is a plain sheet, an OHP sheet, a sheet decolored through a decoloring process, an unused sheet, a reused sheet, or the like. In the case of an apparatus not using toner, the sheet P further includes a thermal sheet, an inkjet sheet, and the like.

The printer section 6 includes an intermediate transfer belt 8. The printer section 6 supports the intermediate transfer belt 8 with a backup roller 9 having a drive section, a driven roller 10 and a tension roller 11, and rotates the intermediate transfer belt 8 in an arrow m direction.

The printer section 6 includes four sets of image forming stations 12Y (yellow), 12M (magenta), 12C (cyan) and 12K (black) respectively corresponding to YMCK, which are arranged in parallel along a lower side of the intermediate transfer belt 8. The printer section 6 includes replenishment cartridges 13Y, 13M, 13C, and 13K for storing toner for replenishment above the image forming stations 12Y, 12M, 12C, and 12K, respectively.

For example, the image forming station 12Y of Y (yellow) has an electrostatic charger 15, an exposure scanning head 16, a developing device 17, and a photoconductor cleaner 18 around a photoconductive drum 14 rotating in the arrow n direction. The image forming station 12Y of Y (yellow) has a primary transfer roller 19 facing the photoconductive drum 14 across the intermediate transfer belt 8.

Three sets of the image forming stations 12M, 12C, and 12K of M (magenta), C (cyan), and K (black) have the same configurations as the image forming station 12Y of Y (yellow). Accordingly, a detailed description of the configurations of three sets of the image forming stations 12M, 12C, and 12K of M (magenta), C (cyan), and K (black) is omitted.

In each of the image forming stations 12Y, 12M, 12C, and 12K, the photoconductive drum 14 is charged by the electrostatic charger 15, exposed by the exposure scanning head 16, and an electrostatic latent image is formed on the photoconductive drum 14. The developing device 17 develops the electrostatic latent image on the photoconductive drum 14 using a two-component developer composed of a carrier and each of toners of Y (yellow), M (magenta), C (cyan) and K (black), respectively.

The primary transfer roller 19 primarily transfers a toner image formed on the photoconductive drum 14 onto the intermediate transfer belt 8. A color toner image is formed by sequentially overlapping toner images of Y (yellow), M (magenta), C (cyan), and K (black) on the intermediate transfer belt 8 by the primary transfer roller 19 with the image forming stations 12Y, 12M, 12C, and 12K. The photoconductor cleaner 38 removes the toner left on the photoconductive drum 14 after a primary transfer.

The printer section 6 includes a secondary transfer roller 20 facing the backup roller 9 across the intermediate transfer belt 8. The secondary transfer roller 20 collectively secondarily transfers the color toner image on the intermediate transfer belt 8 onto the sheet P. The sheet P is fed from the sheet feed cassette section 4 or the manual sheet feed tray 5 along a conveyance path 21 in synchronism with the color toner image on the intermediate transfer belt 8. The belt cleaner 22 removes the toner left on the intermediate transfer belt 8 after a secondary transfer.

The printer section 6 includes a registration roller 23 and a fixing device 25 along the conveyance path 21, and further includes a branch section 26 and an inversion conveyance section 27 on the conveyance downstream side with respect to the fixing device 25. The branching section 26 branches the sheet P after fixing to the sheet discharge section 7 or the inversion conveyance section 27. In a case of double-sided printing, the sheet P is then reversely conveyed in the direction towards the registration roller 23.

The sheet discharge section 7 includes a sheet discharge roller pair 24 composed of an upper roller 24 u and a lower roller 24 d, a placement tray 28 for placing a sheet discharged from the sheet discharge roller pair 24, a sheet presser 29 which is held in a rotatable manner on the sheet discharge side of the upper roller 24 u, an auxiliary tray 30 for holding a sheet rear end of the discharged sheet with the sheet presser 29, an auxiliary tray driving mechanism 31 for driving the auxiliary tray, and a sheet discharge sensor 32 for detecting discharge of the sheet.

With the above configuration, the MFP 1 forms and fixes the toner image based on the document image read by the scanner 2 on the sheet P with the printer section 6, and then discharges the sheet to the sheet discharge section 7. In the following description, it is assumed that a vertical direction with respect to the MFP 1 is a Z-axis direction, a sheet discharge direction is a X-axis direction, and a rotating shaft direction of the sheet discharge roller pair is a Y-axis direction.

FIG. 2 is a block diagram illustrating an example of a configuration of a control system in the MFP 1. The control system of the MFP 1 includes a system controller 100, an input and output controller 110, a sheet conveyance controller 120, an image forming controller 130, and a fixing controller 140, and these control systems are connected with each other via a bus line 150 to operate in cooperation with the system controller 100.

The system controller 100 includes, for example, a CPU 101 that controls the whole MFP 1, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, and an I/F (Interface) 104.

By executing programs scored in the ROM 102 or the RAM 103, the CPU 101 realizes control of the whole MFP including an image forming control, a sheet conveyance control (including sheet discharge control) and the like. The ROM 102 stores control data, and control programs for the image forming control and the sheet conveyance control. The RAM 103 may be mainly used as a working memory for executing control of the whole MFP. The I/F 104 is an input/output interface for communicating with a user terminal and various devices connected to the MFP 1.

The input and output controller 110 controls the control panel 3 and the scanner 2 connected to the input/output control circuit 111. An operator can designate, for example, a sheet size, the number of copies of a document, and the like by operating the control panel 3. The control panel 3 includes a display panel to display a setting and operation state of the MFP 1.

The sheet conveyance controller 120 controls the feed of sheet, the discharge of sheet and the sheet conveyance along with the image formation, and includes a conveyance control circuit 121, a motor group 122, and a sensor group 123. The conveyance control circuit 121 controls the motor group 122 for driving various rollers on the conveyance path, various rollers for image formation, the sheet discharge roller pair 24, and the like. The conveyance control circuit 121 controls the motor group 122 according to a detection result of the various sensor groups 123 arranged on the conveyance path based on a control signal from the CPU 101. In the conveyance control circuit 121, a sheet discharge control circuit 124 for controlling the sheet discharge section 7 is provided. The sheet discharge control circuit 124 is described later in detail.

The image forming controller 130 includes an image forming control circuit 131 for respectively controlling the photoconductive drum 14, the electrostatic charger 15, the exposure scanning head 16, the developing device 17, and the photoconductor cleaner 18 based on a control signal from the CPU 101 to control the image formation.

The fixing controller 140 includes a motor 141 for driving a pressure roller of the fixing device 25, a heater 142 for heating, various temperature sensors 143 for detecting temperature, and a fixing control circuit 144 for performing a fixing temperature control and safety control to execute a fixing control.

The sheet discharge control circuit 124 according to the at least one embodiment is described with reference to FIG. 3. The sheet discharge control circuit 124 includes three control blocks: a sheet detection 301, a sheet presser control 302, and an auxiliary tray control 303.

The sheet detection block 301 detects a passage of the sheet P according to a detection output of the sheet discharge sensor 32 arranged on the conveyance path from the fixing device 25 to the sheet discharge roller pair 24.

The sheet presser control block 302 controls a sheet discharge motor 122 e that drives the sheet discharge roller pair 24 based on the detection output of the sheet discharge sensor 32. By adjusting the conveyance speed of the sheet P to be discharged, an operation time of the sheet presser 29 is controlled.

In accordance with the operation of the sheet presser 29, the auxiliary tray control block 303 controls the auxiliary tray driving mechanism 31 for moving the auxiliary tray 30 to a predetermined position (pressing position) where the auxiliary tray 30 is pressed between the auxiliary tray driving mechanism 31 and the sheet presser 29, or retracting the auxiliary tray 30 from the pressing position. An example in which the auxiliary tray driving mechanism 31 includes an auxiliary tray sensor 122 t and an auxiliary tray motor 123 t is described later.

FIG. 4A and FIG. 4B show examples of installing the sheet presser 29 on the sheet discharge roller pair 24. The sheet discharge roller pair 24 is composed of the upper roller 24 u and the lower roller 24 d. The upper roller 24 u is rotationally driven by a discharge motor 122 e that drives a rotating shaft 41 of the upper roller 24 u, and the lower roller 24 d is driven to rotate by abutting against the upper roller 24 u.

The sheet presser 29 is rotatably attached by a fixing claw 42 on the sheet discharge aide of the rotating shaft 41 of the upper roller 24 u. A rotation angle adjusting claw 43 is provided so as not to contact the lower roller 24 d.

The sheet presser 29 has a length that can press the sheet between the sheet presser 29 and the auxiliary tray 30 below the lower roller 24 d. An attachment position of the upper roller 24 u with respect to the rotating shaft 41 includes a position in a rotating shaft direction where the upper roller 24 u and the lower roller 24 d abut against each other.

In the example in FIG. 4A, four lower rollers 24 d are shown, but one sheet presser 29 is attached with respect to two lower rollers 24 d. In the example in FIG. 4B, the number of the attached sheet pressers 29 may be the same as that of the lower rollers 24 d. The sheet presser 29 is preferably mounted symmetrically with respect to a center (indicated by an arrow) of the sheet P to be discharged.

The sheet presser 29 is lifted up at least by a discharge force of the sheet front end and has a weight capable of pressing the sheet rear end. At a tip of the sheet presser 29, a bent portion 44 for efficiently pressing the sheet rear end between the sheet presser 29 and the auxiliary tray is provided. Therefore, the material of the sheet presser 29 is often a resin material or a metal material which is easy to mold the bent portion 44.

FIG. 5 is a schematic diagram illustrating the auxiliary tray 30 and the auxiliary tray driving mechanism 31 according to at least one embodiment. A wall surface 51 of the placement tray 28 is arranged on the conveyance upstream side by a predetermined distance d with respect to the outer shape of the lower roller 24 d (refer to FIG. 1). This is to prevent the rear end of the discharged sheet from remaining. A tray window 52 is formed on the wall surface 51 of the placement tray in such a manner that the auxiliary tray 30 can rotationally move to a pressing position S. One end of the auxiliary tray 30 is fixed to a rotating shaft 53 arranged below the lower roller 24 d. The rotating shaft 53 is driven by the auxiliary tray motor 123 t, and the auxiliary tray 30 rotationally moves between the pressing position S for pressing the sheet rear end with the sheet presser 29 and a storage position H. For example, an angle of a sensor flag 54 is detected by a photo interrupter type auxiliary tray sensor 122 t, and a rotation angle of the auxiliary tray 30 is controlled.

On at least a part of the auxiliary tray 30, a brake region 56 having a large fractional resistance is formed. This is to improve effects of slowing down or stopping the discharged sheet when the sheet rear end is pressed between the sheet presser 29 and the auxiliary tray 30. The brake region 56 may be formed by attaching a rubber material, a cork material, a felt material, a foaming material or the like to the auxiliary tray 30. Alternatively, the auxiliary tray 30 may be subjected to a surface embossing processing directly.

The auxiliary tray 30 is positioned at a position where it abuts the sheet presser 29. The number of the auxiliary trays 30 may be the same as that of the sheet pressers 29 or may be different from the number of the sheet pressers 29. If the number of the auxiliary trays 30 is increased, the number of tray windows 52 naturally increases, thereby decreasing an area where the sheet rear end contacts with the wall surface 51 of the placement tray. Furthermore, an air resistance at the time of falling of the sheet can be reduced by the tray window 52. This prevents the sheet rear end from remaining. In order to reduce this air resistance, the tray window may have a length in the vertical direction (Z-axis direction).

FIG. 6 is a flowchart for depicting the sheet discharge method. FIG. 7A to FIG. 7D are cross-sectional views of the sheet discharge section showing the sheet discharge state. A sheet discharging method according to the at least one embodiment is described with reference to FIG. 6 and FIG. 7.

In Act 61, the sheet P discharged from the fixing device 25 is detected. As shown in FIG. 7A, a sheet discharge path 71 on the conveyance upstream side with respect to the sheet discharge roller pair 24 (conveyance downstream side with respect to the fixing device 25) includes a sheet discharge sensor 32 and a sheet discharge sensor lever 32L. The sheet discharge sensor lever 32L is a rotatably supported and is returned to its initial rotational position by a spring or the like. For example, the sheet discharge sensor 32 is a photointerrupter type sensor having a light emitting element and a light receiving element. The sheet discharge sensor lever 32L is pushed by the conveyed sheet P, and in this way, the light of the sheet discharge sensor 32 is passed or shielded, thereby detecting the passing of the sheet P. The sheet discharge sensor 32 in FIG. 7 is configured to detect the sheet front end at the start of passing the light and to detect the sheet rear end at the start of shielding the light. Of course, the sheet discharge sensor lever 32L and the sheet discharge sensor 32 may be configured so as to operate in an opposite manner. Act 61 is an operation corresponding to the sheet detection block 301.

In Act 62, as shown in FIG. 7B, the sheet presser 29 is pushed up by the front end of the discharged sheet P. A conveyance time control from detection of the sheet rear end to the front of a nip of the sheet discharge roller pair 24, a conveyance distance control and a sheet pressing control such as a pushing speed of the sheet presser 29 are performed. Act 62 is an operation corresponding to the sheet pressing control block 302.

In Act 63, as shown in FIG. 7B, after detecting the sheet P with the sheet discharge sensor 32, before the sheet rear end passes through the nip of the sheet discharge roller pair 24 (before the sheet rear end is discharged from the sheet discharge roller pair 24), the auxiliary tray 30 is moved to the pressing position S.

In Act 64, as shown in FIG. 7C, the sheet rear end passes through the nip of the sheet discharge roller pair 24 and the sheet rear end is depressed downwards by the dead weight (the load) of the sheet presser 29.

In Act 65, the sheet rear end is pressed between the sheet presser 29 and the auxiliary tray 30. On a part of the auxiliary tray 30, the brake region 56 having a large frictional resistance is formed, thereby slowing down or stopping the discharged sheet with a pressing force and a frictional force in the brake region.

In Act 66, as shown in FIG. 7D, the auxiliary tray 30 is retracted to the storage position H side, and the sheet rear end is released from a pressed (held) state by the sheet presser 29. In Act 67, the sheet P is dropped onto the placement tray 28. The sheet rear end of each of the continuously discharged sheets is slowed down or stopped at the pressing position S and drops in the vertical direction from the pressing position S as the auxiliary tray 30 is retracted. Therefore, it is possible to suppress occurrence of sheet protrusion and occurrence of remaining of the sheet rear end.

Since the wall surface 51 of the placement tray 28 is arranged on the conveyance upstream side with respect to the outer shape of the lower roller 24 d of the sheet discharge roller pair, a gap is generated between the sheet rear end and the wall surface 51. As a result, the opportunity of contacting the sheet rear end with the wall surface 51 decreases, and the sheet falls smoothly in the vertical direction. Therefore, it is possible to further suppress the occurrence of remaining of the sheet rear end. Act 63 and Act 66 correspond to the operation of the auxiliary tray control block 304.

As described above, according to such embodiments, it is possible to suppress the sheet protrusion with respect to the placement tray and to suppress the occurrence of remaining of the sheet rear end, thereby stacking the discharged sheets in an orderly manner.

FIG. 8 is a schematic diagram illustrating the auxiliary tray 30 and the auxiliary tray driving mechanism 31 according to at least one further embodiment. The difference from FIG. 5 is that the auxiliary tray 30 is moved substantially horizontally. The wall surface 51 of the placement tray 26 is arranged on the conveyance upstream side with respect to the outer shape of the lower roller 24 d (refer to FIG. 1). This is to prevent the occurrence of the remaining of the sheet rear end of the discharged sheet and to further align the discharged sheets with the wall surface 51. The tray window 52 for substantially horizontal movement of the auxiliary tray 30 is formed on the wall surface 51 of the placement tray. The auxiliary tray 30 is meshed with a driving gear 81 fixed to the rotating shaft 53 arranged below the lower roller 24 d. The rotating shaft 53 is driven by the auxiliary tray motor 123 t. For example, the auxiliary tray sensor 122 t of the photo interrupter type detects the angle of the sensor flag 54 and the rotation of the driving gear 81 is controlled. As a result, the auxiliary tray 30 moves substantially horizontally between the pressing position S and the storage position H.

The brake region 56 having a large frictional resistance for slowing down or stopping the discharged sheet is formed in at least an area where the sheet is pressed between the auxiliary tray 30 and the sheet presser at the upper part of the auxiliary tray 30. The brake region 56 is formed by attaching a rubber material, a cork material, a felt material, a foaming material or the like to the auxiliary tray 30. Alternatively, the auxiliary tray 30 may be subjected to a surface emboss processing.

FIG. 9A to 9D are cross-sectional views of the sheet discharge section for showing the sheet discharge state. The flowchart for depicting the sheet discharge method is the same as that in FIG. 6, so a duplicate explanation is omitted below, and only different parts are mainly described.

In Act 61, as shown in FIG. 9A, the sheet P discharged from the fixing device 25 is detected. In Act 62, as shown in FIG. 9B, the sheet presser 29 is pushed up by the front end of the discharged sheet P. The conveyance time control from detection of the sheet rear end to the front of a nip of the sheet discharge roller pair 24, the conveyance distance control and the sheet pressing control such as a pushing speed of the sheet presser 29 are performed. In Act 63, as shown in FIG. 9B, after detecting the sheet P with the sheet discharge sensor 32, before the sheet rear end passes through the nip of the sheet discharge roller pair 24 (before the sheet rear end is discharged from the sheet discharge roller pair 24), the auxiliary tray 30 is moved to the pressing position S.

In Act 64, as shown in FIG. 9C, the sheet rear end passes through the nip of the sheet discharge roller pair 24 and the sheet rear end is depressed downwards by the dead weight (the load) of the sheet presser 29. In Act 65, the sheet rear end is pressed between the sheet presser 29 and the auxiliary tray 30, and the discharged sheet is slowed down or stopped by the pressing force and the frictional force in the brake region.

In Act 66, as shown in FIG. 9D, the auxiliary tray 30 is retracted to the storage position H side, and the sheet rear end is released from the pressed (held) state by the sheet presser 29. However, at this time, due to the frictional force of the brake region on the auxiliary tray 30, the sheet rear end is pulled back to the wall surface 51 side of the placement tray 28 along with the retraction operation of the auxiliary tray 30 and then is released from the pressed (held) state after abutting against the wall surface 51 of the placement tray 28.

In Act 67, the sheet P is dropped onto the placement tray 28 after the sheet P abuts against the wall surface 51 of the placement tray. The sheet rear end of discharged sheet is slowed down or stopped at the pressing position S and then pulled back to the retracted auxiliary tray 30, and falls down after abutting against the wall surface 51 of the placement tray 28. A contact area between the sheet rear end and the wall surface 51 is reduced by the tray window 52, thereby decreasing the air resistance at the time of falling. For this reason, the discharged sheet falls down smoothly in the vertical direction. As a result, it is possible to suppress the occurrence of sheet protrusion and the occurrence of remaining of the sheet rear end, thereby stacking the discharged sheets in an orderly manner.

As described above, according to at least one further embodiment, in addition to the effects of some other embodiments, the sheet can be stacked after the sheet rear end abuts against the wail surface of the placement tray. Since the auxiliary tray moves substantially horizontally (i.e., in a substantially horizontal direction), the sheet discharge device can be configured so as to be thinner in the vertical direction than in other embodiments.

FIG. 10 is a flowchart for depicting a method of discharging continuous sheets at a high speed. Flows are respectively added to Act 61 and Act 66 shown in FIG. 6 as Act 61 m and Act 66 m.

In Act 61 m, the sheet rear end is detected by the sheet discharge sensor 32. In Act 62, the sheet presser 29 is pushed up by the front end of the discharged sheet P. In Act 63, a conveyance time or conveyance distance until the sheet rear end is conveyed to the nip front position of the sheet discharge roller pair 24 is calculated, and the auxiliary tray 30 is moved to the pressing position S before the conveyance time or the conveyance distance is reached. In Act 64, the sheet rear end passes through the nip of the sheet discharge roller pair 24 and the sheet rear end is depressed downwards by the dead weight (the load) of the sheet presser 29. In Act 65, the sheet rear end is pressed between the sheet presser 29 and the auxiliary tray 30, and the discharged sheet is slowed down or stopped by the pressing force and the fractional force in the brake region.

In Act 66 m, whether the sheet front end of a succeeding sheet is detected. If the sheet front end of the succeeding sheet is detected (Yes in Act 661), the auxiliary tray 30 is retracted from the pressing position S to the storage position H side (Act 663), and the sheet P being discharged currently is dropped onto the placement tray 28 (Act 67). In a case in which the sheet front end of the succeeding sheet is not detected (No in Act 661), if a predetermined time does not elapse or if the sheet is not conveyed by a predetermined distance (No in Act 662), the flow returns to the process in Act 661 to continue detecting the sheet front end of the succeeding sheet. If the predetermined time elapses or if the sheet is conveyed by the predetermined distance (Yes in Act 662), the auxiliary tray 30 is retracted from the pressing position S to the storage position H side (Act 663), and the sheet P being discharged currently is dropped onto the placement tray 28 (Act 67).

In the high speed discharge process of continuous sheets, a control is performed so as to complete one sheet discharging processing cycle shown in FIG. 10 within a time period from detection of the sheet rear end to the detection of the sheet rear end of the succeeding sheet by the sheet discharge sensor 32.

According to the at least one embodiment, the rotatable sheet presser 29 is provided on the upper roller 24 u of the sheet discharge roller pair, and the auxiliary tray 30 movable between the pressing position S and storage position H is provided below the lower roller 24 d. By temporarily pressing the sheet rear end of the discharged sheet between the sheet presser 29 and the auxiliary tray 30, the discharged sheet is slowed down or stopped at the pressing position S. Thereafter, the auxiliary tray 30 is retracted to the storage position H side, and the sheet is dropped in the vertical direction. In this way, by actively controlling a stacking speed of the discharged sheet, it is possible to greatly improve variation in the sheet stacking caused by the sheet protrusion or the remaining of the sheet rear end. Furthermore, the decrease in the inclination angle of the placement tray contributes to thinning and downsizing of the device.

Although certain embodiments are described above, the present disclosure is not limited by the above embodiments. For example, the brake region is provided on the auxiliary tray, but the brake region may be formed below the sheet retainer 29 or both. Although the sheet presser 29 is arranged on the rotating shaft of the upper roller 24 u, it may be any structure as long as it can be pushed up by the discharged sheet P. In other words, the upper roller 24 u may be appropriately movably held at a predetermined position on the sheet discharge side of the upper roller 24 u.

Although the auxiliary tray driving mechanism 31 is made up of the auxiliary tray sensor 122 t and the auxiliary tray motor 123 t, other configurations thereof may be adopted as long as the same operation can be performed by the auxiliary tray driving mechanism 31.

In the above-described embodiment, there are four contact positions of the upper roller 24 u and the lower roller 24 d, but this is merely an example for convenience of description, and the present disclosure is not limited thereto. The number of sheet pressers or the number of the auxiliary trays is not limited as well.

The MFP is described as an example in certain embodiments; however, the sheet discharge device and the sheet discharge method of the at least one embodiment may be applicable to all the devices for discharging and stacking the sheet-like medium such as a post-processing apparatus of the MFP, a copying machine, a printer, a scanner, an ADF, and the like.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention. 

What is claimed is:
 1. A sheet discharge device, comprising: a sheet discharge roller pair comprising an upper roller and a lower roller; a placement tray, arranged below the sheet discharge roller pair, configured to place a sheet discharged from the sheet discharge roller pair; a sheet presser configured to be held on a sheet discharge side of the upper roller in a movable manner and pushed up by a sheet front end to be discharged, and to depress a sheet rear end with a load of the sheet presser, after the sheet rear end passes through a nip between the sheet discharge roller pair; and an auxiliary tray movable between a first position where the sheet rear end depressed by the sheet presser is held and a second position where the sheet rear end is released from the sheet presser.
 2. The sheet discharge device according to claim 1, wherein the sheet presser is arranged at a position where the upper roller and the lower roller abut against each other.
 3. The sheet discharge device according to claim 1, wherein a brake region having frictional resistance is formed on at least a part of the auxiliary tray.
 4. The sheet discharge device according to claim 1, further comprising: a sheet discharge sensor arranged on a conveyance upstream side with respect to the sheet discharge roller pair; and an auxiliary tray driving mechanism configured to move the auxiliary tray, wherein the auxiliary tray driving mechanism is configured to move the auxiliary tray to a predetermined position when the sheet discharge sensor detects passing of a sheet rear end.
 5. The sheet discharge device according to claim 4, wherein the auxiliary tray driving mechanism is configured to retract the auxiliary tray from the predetermined position when the sheet discharge sensor detects passing of a sheet front end of a succeeding sheet.
 6. The sheet discharge device according to claim 4, wherein one end of the auxiliary tray is fixed to a rotating shaft, and the auxiliary tray driving mechanism is configured to rotate the auxiliary tray by controlling a rotation angle of the rotating shaft.
 7. The sheet discharge device according to claim 4, wherein the auxiliary tray driving mechanism is configured to move the auxiliary tray in a substantially horizontally direction.
 8. The sheet discharge device according to claim 1, wherein a wall surface of the placement tray is arranged on a conveyance upstream aide with respect to an outer shape of the sheet discharge roller pair.
 9. The sheet discharge device according to claim 3, wherein the brake region comprises at least one of a rubber material, a cork material, a felt material, a foaming material, or an embossed surface provided on the auxiliary tray.
 10. A sheet discharge method, including: pushing up a sheet presser movably held on sheet discharge side of an upper roller by a sheet front end discharged from a sheet discharge roller pair comprising the upper roller and a lower roller; depressing a sheet rear end with a load of the sheet presser after the sheet rear end passes through a nip between the sheet discharge roller pair; catching the sheet rear end depressed by the sheet presser with an auxiliary tray when the auxiliary tray is moved to a first position; releasing the sheet rear end from the sheet presser by moving the auxiliary tray to a second position; and dropping the sheet onto a placement tray having a wall surface arranged below the sheet discharge roller pair on a conveyance upstream side.
 11. The sheet discharge method according to claim 10, further comprising arranging the sheet presser at a position where the upper roller and the lower roller abut against each other.
 12. The sheet discharge method according to claim 10, further comprising forming a brake region having frictional resistance on at least a part of the auxiliary tray.
 13. The sheet discharge method according to claim 10, further comprising sensing a sheet discharge via a sensor provided on a conveyance upstream side with respect to the sheet discharge roller pair; driving the auxiliary tray mechanism to move using an auxiliary tray driving mechanism; and causing the auxiliary tray mechanism to move the auxiliary tray to a predetermined position when the sensor detects passing of a sheet rear end.
 14. The sheet discharge method according to claim 13, further comprising retracting the auxiliary tray from the predetermined position when the sensor detects passing of a sheet front end of a succeeding sheet.
 15. The sheet discharge method according to claim 13, further comprising fixing one end of the auxiliary tray to a rotating shaft, and causing the auxiliary tray to rotate by controlling a rotation angle of the rotating shaft.
 16. The sheet discharge method according to claim 13, further comprising moving the auxiliary tray in a substantially horizontally direction.
 17. The sheet discharge method according to claim 10, wherein a wall surface of the placement tray is arranged on a conveyance upstream side with respect to an outer shape of the sheet discharge roller pair.
 18. The sheet discharge method according to claim 12, further comprising: forming the brake region by attaching at least one of a rubber material, a cork material, a felt material, or a foaming material to the auxiliary tray, or creating an embossed surface on the auxiliary tray.
 19. The sheet discharge method according to claim 13, further comprising retracting the auxiliary tray from the predetermined position after elapse of a predetermined time. 